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<div><a href="regex/match_results.html" title="cpp/regex/match results"><span class="t-lines"><span>match_results</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<div><a href="regex/regex_search.html" title="cpp/regex/regex search"><span class="t-lines"><span>regex_search</span></span></a></div>
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<div><a href="regex/regex_replace.html" title="cpp/regex/regex replace"><span class="t-lines"><span>regex_replace</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<tr class="t-nv-h1"><td colspan="5"> Iterators</td></tr>
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<div><a href="regex/regex_iterator.html" title="cpp/regex/regex iterator"><span class="t-lines"><span>regex_iterator</span></span></a></div>
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<div><a href="regex/regex_token_iterator.html" title="cpp/regex/regex token iterator"><span class="t-lines"><span>regex_token_iterator</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code>&lt;regex&gt;</code> </div>
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<p>The regular expressions library provides a class that represents <a href="http%3A//en.wikipedia.com/wiki/Regular_expression" class="extiw" title="enwiki:Regular expression">regular expressions</a>, which are a kind of mini-language used to perform pattern matching within strings. Almost all operations with regexes can be characterized by operating on several of the following objects:
</p>
<ul><li> <b>Target sequence</b>. The character sequence that is searched for a pattern. This may be a range specified by two iterators, a null-terminated character string or <span class="t-lc"><a href="string/basic_string.html" title="cpp/string/basic string">std::string</a></span>.
</li></ul>
<ul><li> <b>Pattern</b>. This is the regular expression itself. It determines what constitutes a match. It is an object of type <span class="t-lc"><a href="regex/basic_regex.html" title="cpp/regex/basic regex">std::basic_regex</a></span>, constructed from a string with special syntax. See <a href="regex/syntax_option_type.html" title="cpp/regex/syntax option type"> syntax_option_type</a> for the description of supported syntax variations.
</li></ul>
<ul><li> <b>Matched array</b>. The information about matches may be retrieved as an object of type <span class="t-lc"><a href="regex/match_results.html" title="cpp/regex/match results">std::match_results</a></span>.
</li></ul>
<ul><li> <b>Replacement string</b>. This is a string that determines how to replace the matches, see <a href="regex/match_flag_type.html" title="cpp/regex/match flag type"> match_flag_type</a> for the description of supported syntax variations. 
</li></ul>
<table id="toc" class="toc"><tr><td>
<div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="regex.html%23Main_classes"><span class="tocnumber">1</span> <span class="toctext">Main classes</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="regex.html%23Algorithms"><span class="tocnumber">2</span> <span class="toctext">Algorithms</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="regex.html%23Iterators"><span class="tocnumber">3</span> <span class="toctext">Iterators</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="regex.html%23Exceptions"><span class="tocnumber">4</span> <span class="toctext">Exceptions</span></a></li>
<li class="toclevel-1 tocsection-5"><a href="regex.html%23Traits"><span class="tocnumber">5</span> <span class="toctext">Traits</span></a></li>
<li class="toclevel-1 tocsection-6"><a href="regex.html%23Constants"><span class="tocnumber">6</span> <span class="toctext">Constants</span></a></li>
<li class="toclevel-1 tocsection-7"><a href="regex.html%23Example"><span class="tocnumber">7</span> <span class="toctext">Example</span></a></li>
</ul>
</td></tr></table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Main classes">edit</a>]</span> <span class="mw-headline" id="Main_classes">Main classes</span>
</h3>
<p>These classes encapsulate a regular expression and the results of matching a regular expression within a target sequence of characters.
</p>
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<div><a href="regex/basic_regex.html" title="cpp/regex/basic regex"> <span class="t-lines"><span>basic_regex</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</td>
<td>   regular expression object  <br> <span class="t-mark">(class template)</span> 
</td>
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<div><a href="regex/sub_match.html" title="cpp/regex/sub match"> <span class="t-lines"><span>sub_match</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>   identifies the sequence of characters matched by a sub-expression  <br> <span class="t-mark">(class template)</span> 
</td>
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<div><a href="regex/match_results.html" title="cpp/regex/match results"> <span class="t-lines"><span>match_results</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</td>
<td>   identifies one regular expression match, including all sub-expression matches  <br> <span class="t-mark">(class template)</span> 
</td>
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</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Algorithms">edit</a>]</span> <span class="mw-headline" id="Algorithms">Algorithms</span>
</h3>
<p>These functions are used to apply the regular expression encapsulated in a regex to a target sequence of characters.
</p>
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<div><a href="regex/regex_match.html" title="cpp/regex/regex match"> <span class="t-lines"><span>regex_match</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>   attempts to match a regular expression to an entire character sequence  <br> <span class="t-mark">(function template)</span> 
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<div><a href="regex/regex_search.html" title="cpp/regex/regex search"> <span class="t-lines"><span>regex_search</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>   attempts to match a regular expression to any part of a character sequence  <br> <span class="t-mark">(function template)</span> 
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<td>  <div class="t-dsc-member-div">
<div><a href="regex/regex_replace.html" title="cpp/regex/regex replace"> <span class="t-lines"><span>regex_replace</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   replaces occurrences of a regular expression with formatted replacement text  <br> <span class="t-mark">(function template)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Iterators">edit</a>]</span> <span class="mw-headline" id="Iterators">Iterators</span>
</h3>
<p>The regex iterators are used to traverse the entire set of regular expression matches found within a sequence.
</p>
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<tr class="t-dsc-sep">
<td colspan="2">
</td>
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<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="regex/regex_iterator.html" title="cpp/regex/regex iterator"> <span class="t-lines"><span>regex_iterator</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   iterates through all regex matches within a character sequence  <br> <span class="t-mark">(class template)</span> 
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
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<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="regex/regex_token_iterator.html" title="cpp/regex/regex token iterator"> <span class="t-lines"><span>regex_token_iterator</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   iterates through the specified sub-expressions within all regex matches in a given string or through unmatched substrings  <br> <span class="t-mark">(class template)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Exceptions">edit</a>]</span> <span class="mw-headline" id="Exceptions">Exceptions</span>
</h3>
<p>This class defines the type of objects thrown as exceptions to report errors from the regular expressions library.
</p>
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<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="regex/regex_error.html" title="cpp/regex/regex error"> <span class="t-lines"><span>regex_error</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   reports errors generated by the regular expressions library  <br> <span class="t-mark">(class)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Traits">edit</a>]</span> <span class="mw-headline" id="Traits">Traits</span>
</h3>
<p>The regex traits class is used to encapsulate the localizable aspects of a regex.
</p>
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<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="regex/regex_traits.html" title="cpp/regex/regex traits"> <span class="t-lines"><span>regex_traits</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   provides metainformation about a character type, required by the regex library  <br> <span class="t-mark">(class template)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Constants">edit</a>]</span> <span class="mw-headline" id="Constants">Constants</span>
</h3>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in  namespace <code>std::regex_constants</code> </div>
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="regex/syntax_option_type.html" title="cpp/regex/syntax option type"> <span class="t-lines"><span>syntax_option_type</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   general options controlling regex behavior  <br> <span class="t-mark">(typedef)</span> 
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<td colspan="2">
</td>
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<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="regex/match_flag_type.html" title="cpp/regex/match flag type"> <span class="t-lines"><span>match_flag_type</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   options specific to matching  <br> <span class="t-mark">(typedef)</span> 
</td>
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<tr class="t-dsc-sep">
<td colspan="2">
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<td>  <div class="t-dsc-member-div">
<div><a href="regex/error_type.html" title="cpp/regex/error type"> <span class="t-lines"><span>error_type</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   describes different types of matching errors  <br> <span class="t-mark">(typedef)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span>
</h3>
<div class="t-example">
<p> <span style="font-size:0.7em; line-height:130%">Note: only upcoming GCC 4.9 supports C++11 regexes. Please select clang 3.4 (C++11) at the moment</span>
 </p>
<div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;iterator&gt;</span>
<span class="co2">#include &lt;string&gt;</span>
<span class="co2">#include &lt;regex&gt;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <a href="string/basic_string.html"><span class="kw1045">std::<span class="me2">string</span></span></a> s <span class="sy1">=</span> <span class="st0">"Some people, when confronted with a problem, think "</span>
        <span class="st0">"<span class="es1">\"</span>I know, I'll use regular expressions.<span class="es1">\"</span> "</span>
        <span class="st0">"Now they have two problems."</span><span class="sy4">;</span>
 
    <a href="regex/basic_regex.html"><span class="kw1680">std::<span class="me2">regex</span></span></a> self_regex<span class="br0">(</span><span class="st0">"REGULAR EXPRESSIONS"</span>,
            <a href="regex/syntax_option_type.html"><span class="kw1712">std::<span class="me2">regex_constants</span><span class="sy4">::</span><span class="me2">ECMAScript</span></span></a> <span class="sy3">|</span> <a href="regex/syntax_option_type.html"><span class="kw1708">std::<span class="me2">regex_constants</span><span class="sy4">::</span><span class="me2">icase</span></span></a><span class="br0">)</span><span class="sy4">;</span>
    <span class="kw1">if</span> <span class="br0">(</span><a href="regex/regex_search.html"><span class="kw1693">std::<span class="me2">regex_search</span></span></a><span class="br0">(</span>s, self_regex<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
        <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"Text contains the phrase 'regular expressions'<span class="es1">\n</span>"</span><span class="sy4">;</span>
    <span class="br0">}</span>
 
    <a href="regex/basic_regex.html"><span class="kw1680">std::<span class="me2">regex</span></span></a> word_regex<span class="br0">(</span><span class="st0">"(<span class="es1">\\</span>S+)"</span><span class="br0">)</span><span class="sy4">;</span>
    <span class="kw4">auto</span> words_begin <span class="sy1">=</span> 
        <a href="regex/regex_iterator.html"><span class="kw1698">std::<span class="me2">sregex_iterator</span></span></a><span class="br0">(</span>s.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, s.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, word_regex<span class="br0">)</span><span class="sy4">;</span>
    <span class="kw4">auto</span> words_end <span class="sy1">=</span> <a href="regex/regex_iterator.html"><span class="kw1698">std::<span class="me2">sregex_iterator</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
 
    <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"Found "</span>
              <span class="sy1">&lt;&lt;</span> <a href="iterator/distance.html"><span class="kw551">std::<span class="me2">distance</span></span></a><span class="br0">(</span>words_begin, words_end<span class="br0">)</span>
              <span class="sy1">&lt;&lt;</span> <span class="st0">" words<span class="es1">\n</span>"</span><span class="sy4">;</span>
 
    <span class="kw4">const</span> <span class="kw4">int</span> N <span class="sy1">=</span> <span class="nu0">6</span><span class="sy4">;</span>
    <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"Words longer than "</span> <span class="sy1">&lt;&lt;</span> N <span class="sy1">&lt;&lt;</span> <span class="st0">" characters:<span class="es1">\n</span>"</span><span class="sy4">;</span>
    <span class="kw1">for</span> <span class="br0">(</span><a href="regex/regex_iterator.html"><span class="kw1698">std::<span class="me2">sregex_iterator</span></span></a> i <span class="sy1">=</span> words_begin<span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> words_end<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
        <a href="regex/match_results.html"><span class="kw1690">std::<span class="me2">smatch</span></span></a> match <span class="sy1">=</span> <span class="sy2">*</span>i<span class="sy4">;</span>
        <a href="string/basic_string.html"><span class="kw1045">std::<span class="me2">string</span></span></a> match_str <span class="sy1">=</span> match.<span class="me1">str</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
        <span class="kw1">if</span> <span class="br0">(</span>match_str.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&gt;</span> N<span class="br0">)</span> <span class="br0">{</span>
            <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"  "</span> <span class="sy1">&lt;&lt;</span> match_str <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
        <span class="br0">}</span>
    <span class="br0">}</span>
 
    <a href="regex/basic_regex.html"><span class="kw1680">std::<span class="me2">regex</span></span></a> long_word_regex<span class="br0">(</span><span class="st0">"(<span class="es1">\\</span>w{7,})"</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="string/basic_string.html"><span class="kw1045">std::<span class="me2">string</span></span></a> new_s <span class="sy1">=</span> <a href="regex/regex_replace.html"><span class="kw1694">std::<span class="me2">regex_replace</span></span></a><span class="br0">(</span>s, long_word_regex, <span class="st0">"[$&amp;]"</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> new_s <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">Text contains the phrase 'regular expressions'
Found 19 words
Words longer than 6 characters:
  people,
  confronted
  problem,
  regular
  expressions."
  problems.
Some people, when [confronted] with a [problem], think 
"I know, I'll use [regular] [expressions]." Now they have two [problems].</pre></div></div> 
</div>

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